MULTICENTER EVALUATION OF THE THROMBOTEST INTERNATIONAL SENSITIVITY INDEX USED WITH A STEEL BALL COAGULOMETER

Aim-To compare the International Sensitivity Index (ISI) of the Thromb otest reagent used with a steel ball coagulometer (KC) to the ISI of t he same reagent used with the manual (tilt tube) technique. Methods-Th e study was carried out by eight laboratories using their own KC instr ument and method of testing. All laboratories used the same batch of T hrombotest to determine the clotting times of fresh blood samples from 20 local healthy volunteers and 60 patients on long term oral anticoa gulant therapy. KC clotting times were plotted against manual clotting times on double logarithmic scales. Orthogonal regression Lines were calculated to assess the ISI. Results-In two laboratories the ISI of t he KC method was lower than that of the manual method; these differenc es, however, were 2% or less. In the other laboratories no clinically important differences were observed between ISI values obtained. Howev er, the clotting times determined with the KC methods were shorter tha n the manual values. Conclusions-The ISI of Thrombotest determined wit h the KC methods was very similar to the manual value. Therefore, use of the ISI value supplied by the manufacturer without adjustment is ju stified. The mean normal prothrombin time, however, must be determined locally.